Cellulosic structures and method of preparing same



Patented Feb. 16, 1937 UNITED STATES CELLULOSIC STRUCTURES AND METHOD OF PREPARING SAME Percy Morgan Clark, New Brunswick, N. J., as! slgnor, by mesne assignments, to E. I. du Pont de Nemours & Company, Wilmington, corporation of Delaware DeL, a

No Drawing. Application February 16, 1935,

Serial No. 6,879

7 Claims. (01.106-40) This invention relates cellulosic structures and more particularly it relates to cellulosic structures in the formof filaments, threads, fab- 1 rics, sheets, films, caps, tubing and the like, havluster and/or being more delusterlng oils have been used .for this purpose with more or less success to produce a delustered and/or opaque structure. Among the inorganic pigments most. commonly used may be mentioned titanium oxide. While this pigment has excellent covering power and can be used in small quantities to produce low luster and/or opaque products, its use is objectionable for other reasons. For instance, loss in strength is particularly noticeable in rayon prepared from a solution having incorporated therein titanium oxide, when this rayon is later submitted to the bleaching process in the presence of light. The side of the bobbin,cake or skein of rayon thread which is exposed to the light during the bleaching process will be found to have considerably less strength than the portions of the cake or bobbin which were not exposed to the light.

It has also been found that cellulosic pellicles such as bottle caps and the like, which .are

, opaquedwith titanium oxide, and dyed-with direct dyestufls, after which they are stored in a glycerin-water mixture prior to their use,, are

' found to be subiect'to very material and objectionable, fading. The fading is found to be accelerated by exposure to light and takes place to a considerable extent even in the absence of light.

This fading has been definitely attributed to the presence of the titanium oxide since the same i does not take place in the absenceof such pigment.

Stfll' another objectionable characteristic of titanium oxide is the tendency thereof todarken in the presence of light but with the exclusion 01 air or other oxidizing agent when in contact with certain reducing agents, such as, for example, cellulose, glycerin. grape sugar, niannite and the like. I I

Various other inor anic pigments have been found to be unsuitable asopaquing agents and/or delusterants in cellulosic materials by reason of the fact that they are reactive, soluble or partially soluble in the baths used in the processing of the cellulosic materials. Still other inorganic pigments, such as, for example, white lead, have been found to be entirely unsuitable for cellulosic materials by reason of their toxicity.

The process of this invention particularly contemplates the manufacture of delustered and/or opaque cellulosic structures from viscose solutions. However, other cellulosic solutions or dispersions for the production of regenerated cellulose or cellulose derivatives, such as cuprammonium cellulose solutions; nitrocellulose; organic ester solutions, for example, cellulose acetate; cellulose ethers, for example, benzyl cellulose may also be used with the opaquingand/or delustering agents described herein for the production of deiustered and/or opaqued cellulosic structures. It is therefore an object of this invention to produce delustered and/or opacifled cellulosic structures which are not substantially weakened by exposure to light during bleaching, or subsequently by exposure to light in the moist or dry condition in ordinary use of the structures.

It is another object of this invention to prepare delustered and/or opaclfled cellulosic structures which after dyeing will be fast to light.

It is another object of this invention to prepare 'a delustered and/or opaclfled cellulosic structure having incorporated therein a stable,

white, delustering or opacifying agent.

It is a still further object of this invention to prepare a delustered and opacifled cellulosic structure which may 'be dyed and stored in aqueous glycerin solutions without fading.

It is still another object of this invention to produce delustered and/or opacified cellulosic structures, the luster and opacity of which are substantially insensitive to processing baths and reagents used in the making of the cellulosic structures and which are used in the processing thereof in textile trades,,etc;, and in which the delustering and/or opacifying' agent is non-toxic.

Other objects of the invention will appear hereinafter.

These objects are accomplished in general by incorporating v an insoluble, white, metallic titanate pigment into the cellulosic material from which the cellulosic structure is to be produced. The pigment will have a refractive index differing by at least 0.1 from the mean index of refraction of the substance comprising the mass of the cellulosic structure. The titanate pigment l is preferably ground to an extremely small size which is dispersed into the cellulosic liquid from which the cellulosic structure is to be made, and the cellulosic structure is extruded, molded, or cast in the manner well known in the art. v

As the insoluble, metallic titanate pigment (which will preferably be white) contemplated by this invention, the-following may be named as representativei White insoluble titanates of the formula MTiOa and MI2TiO4, where M is a bivalent metal, the oxide of which is white, such as for example, alkaline earth metal titanates including barium titanate, BaTiOs, magnesium titanate, MgTiOa, calcium titanate, CaTiOa, and other metal titanates, such as 'zinc titanate, ZnzTiOatitanates of the general formula MTiOs or MO. TiOz, usually considered as normal titanates; basic and acid titanates such as may be represented by the intended to be included within the scope of this invention. Titanates of metals which have a valence other than two, and which are insoluble in the cellulosic structure, and otherwise conform to the requirements of a good delusterant, may also be used.

The proportion of delustering or opacifying agent to be incorporated into the cellulosic solution may vary within wide limits, the concentration thereof depending upon the amount which can be incorporated without impairing the solution from the standpoint of spinning or casting conditions and physical properties of the resultant cellulose materials. The type of cellulosic material furthermore may more or less limit the amount of inorganic pigment which may be incorporated therein. 'The ratio of pigment to cellulose in the final product will vary according to the degree of opacity and/or luster de-' 40 sired. For example, in caps, bands and-other pellicles, the proportion of titanate which may be incorporated therein may range between 5 to 50%, base l on the weight of the cellulose in the solution or 0.35% to 3.5%, based on the weight formulae (MOhTiOz and MO.(TiOz)x are also 7 well-known method, such as grinding in a colloid mill or pebble mill or in the form of a suspension or emulsion prepared with or without the assistance of suitable dispersing agents or protective colloids,-e. g. soaps, sulphonated oils, alkyl naph- 5 thalene sulphonic acid salts (Nekal), sodium caseinate, etc., or combinations thereof.

Although the preferred embodiments of this invention contemplate the incorporation of th low luster-inducmg agent in the solution, at some 10 time prior to extrusion or casting thereof, satisfactory results may be secured also by applying the pigment to a previously formed cellulosic structure. In other words, the low luster-inducing and/or opaquing agent may be incorpol5 rated in the final cellulosic structure by an after treatment.

The following detailed examples illustrate specifically methods for carrying out the process of the invention. It is to be understood, however, that the specific details set forth in these examples are not in any way to limit the scope of the invention.

Example I The undyed caps have a particularly pure white color, because magnesium titanate lacks the yelof a cellulosic solution containing 7% cellulose..

merely to assume a translucent appearance, the

.-usual manner.

erally smaller than that which may be used in caps, films and other pellicles. -The proportion of inorganic pigments which may be incorporated into cellulosic solutions for threadand fibers may vary between 0.001 to 1% based upon a cellulosic solution containing approximately 7% cellulose. I

v The low luster-inducing and/or opaquing agent may be added to the. cellulosic solution at any stage in the course ofthe preparation of the solution priorto the actual spinning or casting of the cellulosic product. Itmay be added directly, if the particle size is satisfactory, or after suitable adjustment of the particle size by any low tone often associated with other known mag- :40 nesium compounds. These caps arehighly resistant to darkening on exposure to light. The dyed caps are resistant to fading when stored in a solution of water and glycerin.

Example II then added to viscose to give a viscose solution containing 0.04% barium titanate and 7% cellu- -50 lose. This viscose is then spun into threads and washed, desulfured, bleached and dried in the Example III A sample of zinc titanate is ground with 1% sodium pyrophosphate and an equal weight of water until well dispersed. Suflicient of this dispersion is used in making up viscose so that the resulting solution contains 0.15% zinc titanate and 7% cellulose. This viscose is spun into threads, coagulated, regenerated and bleached in the usual manner.

.The productof the last two examples is characterized by a pleasing, uniform, chalk white appearance. 1g: rayon is resistant to weakening causedby ex sure to light during the bleaching process. It dyes uniformly and when so dyed, is not subject to fading induced bythe presence of the pigment as is the case with titanium oxide. m

If desired, the titanates may be used in combination with other low luster inducing agents. such as mineral oil,' halogenated diphenyls or halogenated naphthalenes, or other organic delusterants and/or inorganic pigments.

Cellulosic filaments or pellicles, delustered and/or opaqued with titanate pigments, have been found to yield structures of exceptionally uniform luster and/or opaqueness. This is a matter of great importance in the preparation of commercial products since comparatively minor variations in luster may impair the commercial utility of large portions of rayon, for example; These titanate pigments have furthermore been found to be non-toxic.

"usual direct colors and stored in glycerin-water mixtures without excessive fading. This has been found to be a matter of prime importance in themanufacture of caps and bands where the latter must be stored or shipped in glycerinwater mixtures or the like. Furthermore, viscose rayon delustered with the titanate pigments may be bleachedin the light without loss in strength of the thread and the same may be exposed tolight in its moistened or dry condition without deterioration as is the case with T10: delustered rayon.

.The characteristics of the titanate' pigments contemplated as within the scope of this invention may be attributedto the surprising stability oi the titanate pigments in the presence of reducting agents. Whereas, known titanium compounds, such as, rorexample, titanium oxide..

are readilyreduced to highly colored trivalent titanium products under certain conditions, the titanate pigments are stable under such conditions.. This can be strikingly shown by calcination of the pigment in a reducing atmosphere or by a glycerin paste of the pigment spread on aglass slidetosunlight for from ito 2 hours. Magnesium and zinc titanates will be tound to be particularly stable .under the latter conditions. ,Commerciai barium titanate is.

somewhat less so, but its small light sensitivity may be due to a small proportion of free titanium oxide which is usually present in commercial samples. Calcium titanate is actually whitened,

by calcining the same in a reducing atmosphere.

5. The white,.insoluble, inorganic titanates have powerswhicharemuchhigherthan opacifying mostotberpigmentssothattheirusehasbem immd to be economical.

Since it is obvious that various changes and modifications may be made insthe above description without departing from the nature and spirit of the invention, it is to be understood that the invention is. not to be limited thereto except as set forth in the appended claims.

I claim:

1. A hollow gel cellulosic pellicle adapted to shrink by loss of contained water, having incorporated therein a white, insoluble metal titanate and being dyed with a direct dyestuif, said titanate remaining substantially unaffected in the presence of bleaching solution and upon exposure to light, and being present in a quantity suflicient to substantiallyprevent said dyestui! from fading when subjected to the action of an aqueous solution of glycerin.

2. A hollow gel regenerated cellulose pellicle adapted to shrink by loss of contained water, having incorporated thereina white, insoluble metal titanate and being dyed with a direct dyestuii, said titanate remaining substantially unaffected in the presence of bleaching solution and upon exposure to light, and being present in a quantity suflicient to substa'ntialLv prevent said dyestufi from fading when subjected to the action of an aqueous solution oi glycerin.

3. A hollow gel regenerated cellulose pellicle adapted to shrink by loss of contained water, having incorporated therein a white, insoluble divalent metal titanate and being dyed with a direct'dyestufl, said titanate remaining substantially unaffected in the presence of bleaching solution and upon exposure to light, and being present in a quantity sufllcient to substantially prevent said dyestui! from fading when subjected to the action of an aqueous solution of lycerin.

4. 'I'hepellicleot claim3characterizedinthat the said titanate is barium titanate.

5. Thepellicleotclaimiiinthat the said titanate is magnesium titanate.

6. The pellicle of claim 8 characterized in that said titanate is nine titanate.

7. The process of preparing hollow gel regenerated cellulose pellicles adapted to shrink by loss 01 contained water, which comprises dispersing finely divided barium titanate in water containing sodium pyrophosphate, commingling said dispersionwithviscoseinsuchproportions that the latter contains 1.5% barium titanate and 1% 

